Assembly for securing a wear

ABSTRACT

A wear member for excavating equipment and which is particularly suited for a dredge cutterhead that includes a curved abutting surface that abuts a complementary curved bearing surface on the base. The curved bearing surfaces are able to maintain substantially full contact with each other under transverse loading. The base and adapter further having a plurality of complementary stops for resisting relative movement between them.

FIELD OF THE INVENTION

The present invention pertains to an assembly for securing a wear memberto excavating equipment. In one advantageous arrangement, the wearmember is particularly suited for use in attaching an adapter to adredge cutterhead. The present invention also pertains to an improvedconstruction for welding a member to a support structure such as, forexample, an arm of a dredge cutterhead or a lip of an excavating bucket.

BACKGROUND AND SUMMARY OF THE INVENTION

Dredge cutterheads are used for excavating earthen material that isunderwater, such as a riverbed. One example of a dredge cutterhead isillustrated in FIG. 17. In general, a dredge cutterhead includes severalarms 11 that extend forward from a base ring 16 to a hub 23. The armsare equally spaced about the base ring and formed with a broad spiralabout the central axis of the cutterhead. Each arm is provided with aseries of spaced apart teeth 12 to dig into the ground.

In use, the cutterhead is rotated about its central axis to excavate theearthen material. To excavate the desired swath of ground the cutterheadis moved side-to-side as well as forward. On account of swells and othermovement of the water, the cutterhead will also tend to move up anddown, and periodically impact the bottom surface. As a result of thisunique cutting action, the teeth of a dredge cutterhead experience heavytransverse as well as axial loading and heavy impact jacking loads thatthrust the tooth up, down and sideways. The heavy transverse loading ofthe tooth is further engendered by the operator's inability to see theground that is being excavated underneath the water. Unlike otherexcavators (e.g., a front end loader), the operator of a dredgecutterhead cannot effectively guide the cutterhead along a path to bestsuit the terrain to be excavated.

Due to the rotative digging action of the cutterhead, each toothpenetrates the ground on the order of 30 times a minute as compared toabout 1 time a minute for mining teeth. As a result, the teethexperience a great amount of wear during use. It is desirable thereforefor the teeth to be easily removed and installed to minimize downtimefor the cutterhead. As is common with wear assemblies for excavatingequipment, dredge teeth comprise a plurality of integrally connectedparts so as to minimize the amount of material needing replacement,i.e., only the worn components need to be replaced.

In the example of FIG. 17, each tooth includes a base 18, an adapter 13,a point or tip 17, and a lock 29. The base 18 is cast on the arm 11 at aparticular location and orientation to maximize digging. Adapter 13includes a rear end 22 that is received in a socket 14 defined in thebase, and a forwardly projecting nose 15 to hold the point 17. Aremovable lock 29 is provided to facilitate the required frequentreplacement of the tooth points 17. The adapter is held in the socket bya large fillet weld about the circumference of the rear end 22. In otherknown dredge cutterheads 1, the adapter 2 is bifurcated to define a pairof legs that are configured to wrap about the arm 3 (FIG. 18). Theseadapters are welded directly to the arm without a base member.

Although the tooth points require the most frequent replacement in adredge cutterhead, the adapters still wear and need periodicreplacement. However, replacing even a single adapter on a dredgecutterhead is a long process. The welded adapter must first be cut offwith a torch. Then, portions of the arm and base that were damaged bythe removal of the adapter must be repaired and rebuilt. Finally, a newadapter is welded into place. This process typically entails 10-12man-hours per adapter. Hence, a lengthy delay in a dredging operation isunavoidable even when replacing only a single adapter. Moreover, in viewof this lengthy delay, an operator will often wait until severaladapters need replacement to take the cutterhead out of operation. As aresult, the actual delay in operation that usually occurs is longer.Indeed, with a typical cutterhead having 50-60 teeth a rebuildingprocess of the entire cutterhead could require more than 600 man-hours.In an effort to avoid substantial loss of dredging time, most dredgingoperations maintain three or four cutterheads so that the entirecutterhead can be exchanged when one or more adapter needs to bereplaced, the cutterhead needs to be rebuilt, or if the cutterheadbreaks. However, a cutterhead is expensive. The maintaining of extracutterheads that are not used, but held only when the one in use isserviced is an undesirable use of resources.

In one aspect of the present invention, the adapter is mechanicallyattached to the arm for easy installation and removal. The adapter isheld to a base on the arm solely by a mechanical construction withoutthe need for welding the adapter. In the preferred construction, thebase and adapter are formed with complementary coupling configurationsto prevent release of the adapter from the base except in a releasedirection. A removable lock is used to prevent undesired release of theadapter from the base in the release direction. With a mechanicalattachment, the adapter can be easily replaced by simply removing thelock and moving the adapter in the release direction. There is no weldto be cut, no need to repair the base and arm, and no re-application ofa weld. As opposed to 10-12 man-hours for replacing a welded adapter, amechanically attached adapter in accordance with the present inventioncan be changed in as little as 10 minutes. This is a dramaticimprovement which hot only substantially reduces downtime for thecutterhead, but can also make the elimination of an entire sparecutterhead at the dredging site possible. As a result, instead oftypically needing three or four cutterheads at a dredge site, only twoor three may be needed.

In a preferred construction of the present invention, the adapterincludes a generally T-shaped slot that receives acomplementarily-shaped tongue on the base, and an opening for receivinga lock. The lock, when inserted into the opening, opposes a wall of thebase and a wall of the opening to prevent release of the tongue andslot, and thereby holds the adapter to the base.

It is common for adapters of various excavators, such as a front endloader, to be mechanically attached to the excavating bucket. Forexample, U.S. Pat. No. 5,653,048 discloses an adapter with a T-shapedslot that receives a T-shaped boss welded to the lip of an excavatingbucket. A lock is fit within an opening in the top of the adapter toprevent loss of the adapter from the lip. A bearing surface is formed atthe front end of the boss to provide axial support for the adapter.While this construction well supports an adapter on an excavatingbucket, it is not well suited for use on a dredge cutterhead.

In an excavating bucket, the teeth are primarily subjected to axialloading as the bucket is driven forward through the ground. However, asdiscussed above, the teeth on a dredge cutterhead are subjected to heavyand frequent transverse loads due to the manner in which the cutterheadis operated. In the noted '048 patent, the adapter 4 is slid onto theboss 5 with a slight side clearance for ease of assembly. Theapplication of a large side load L applied against the tooth point 6tends to rotate the adapter about the received boss to the extent of thedefined clearance between the parts (FIG. 16). This rotation of theadapter results in the generation of resistant forces R1-R4 and highstresses being generated through essentially “point” contacts in thecorners of the assembly. Although true point contact is impossible, theterm is used to identify large applications of force over a relativelysmall area. In particular, the application of large forces R2, R3 at“points” on the front of the base and the lock 7 place exceptionallyhigh levels of stress on the components. Such high stress levels, inturn, cause greater wearing of the parts at these locations and ashortened usable life of the parts. The increased wearing also enlargesthe clearance space, which can lead to rattling of the components duringuse. Such rattling of the parts further quickens wearing of the parts.

In ordinary digging, such as with a front end loader, fines becomeimpacted between the adapter and base so that rattling is reduced oreliminated even when wearing has created large gaps between the parts.However, in a dredging operation, the water sweeps the fines in and outof the gaps, and prevents the build up of fines between the parts. Sincethe gaps between the parts would ordinarily remain in a dredgingoperation, an adapter mechanically attached to a boss on a dredgecutterhead by a known construction would continually rattle against theboss and repeatedly apply large loads in point contacts along the frontand rear of the adapter. Moreover, since the fines are constantly sweptinto and out of the gaps between the parts with the water, the fineswould actually function as a grinding compound on the parts to furtherexacerbate wearing of the parts. Consequently, adapters for dredgingoperations have not before been mechanically attached to the dredgecutterhead arms.

However, these shortcomings are overcome in the present invention sothat adapters in dredging teeth can be mechanically attached to thearms. In particular, the front of the base is curved and in contact witha complementary abutment of the adapter. As a result, when side loadspush the adapter in a rotative manner, the arcuate shape of the bearingsurfaces enables the surfaces to remain in substantially full flushcontact with each other. This full contact arrangement as opposed to apoint contact greatly reduces the stress otherwise experienced in thecorners of the components. Rather than having high loads appliedessentially as point contacts, the loads are spread over substantiallythe entire bearing surface to greatly minimize the stress in the partsand, in turn, substantially lengthen the usable life of the parts.

In a preferred construction, the arcuate bearing surfaces definespherical segments to maintain substantially full contact between thebearing surfaces of the adapter and the base under both horizontal andvertical transverse loading. In addition, the rear bearing surface ofthe base and the front of the lock are also preferably formed withsimilar arcuate surfaces to likewise maintain substantially full contactbetween the lock and the base. Preferably, the radii of curvature forthe bearing surface at the front and rear of the adapter originate fromthe same point.

In another aspect of the invention, the base and adapter are formed witha front bearing surface that is subdivided to define a transverse stopto resist rolling of the adapter on the base, which in turn reduceswearing of the parts.

In one other aspect of the invention, the base and adapter are formedwith axially spaced complementary stops to resist relative sliding ofthe adapter on the base, and thereby reduce wearing of the componentsduring use.

In another aspect of the invention, a wear member for use withexcavators other than dredge cutterheads could also be benefited byincorporating the curved and/or multiple bearing surfaces describedabove for the adapter.

In another aspect of the present invention, the lock is formed totighten the connection between the base and adapter. A tightenedassembly alleviates rattling and thereby lengthens the useful life ofthe components. The above-noted '048, patent discloses a lock with athreaded plug that tightens the adapter on the boss. Nevertheless, thestress and strains of digging can work to loosen even an initiallytightened arrangement such that the adapter will still shift and rattleagainst the base resulting in increased wear, particularly with the highfrequency of penetration and varied loading of teeth on a dredgecutterhead. Further, with a loosening assembly, there would be nothingin a water environment to prevent the components from rattling duringuse.

Therefore, in accordance with another aspect of the present invention,the lock further includes a resilient element that cooperates with anactuator to maintain a tight engagement between the adapter and baseeven after loads have introduced wear between the parts. The resilientelement is sandwiched between a pair of rigid members. The actuatorinitially pulls the adapter into a tight engagement with the base anddraws the rigid members together to compress the resilient element. Aslooseness begins to develop in the assembly due to wearing, theresilient element expands to dampen any shifting or rattling of theadapter on the base and thereby maintain a tight engagement between thetwo components. The rigid members also preferably have at least one stopthat prevents excessive compression of the resilient element. In thisway, the rigid members initially form a rigid lock that is tightly setbetween the adapter and the base, and which also protect the internalresilient element from premature failure on account of being overloaded.

As discussed above, the arms in a dredge cutterhead have a broadspiraling configuration. As a result, the teeth each project from thearm at a unique orientation to maximize digging. Since the teeth aremounted in different orientations on the arm, care must be taken toensure that each adapter is properly positioned on the arm. Thisadditional positioning procedure further lengthens the time needed toinstall new adapters in past cutterheads. In the example illustrated inFIG. 17, a resin is poured into the socket to harden around the firstmounted adapter to thus form a recess adapted to properly orientsuccessive adapters for the dredging operation. Nevertheless, thisdesign still requires a careful, time-consuming procedure to initiallyplace the adapters properly on the arm as well as the extra work ofpouring and curing the resin.

As can be appreciated, since there is no guiding base in the directwelding of adapters to the arms, such as in FIG. 18, it is nearlyimpossible to properly position each of the adapters for maximum diggingefficiency. Moreover, arms on a dredge cutter do not have a uniformconfiguration as they extend from the base ring to the hub. To avoid thecost and trouble of having to make a specifically shaped adapter tocustom fit each designated location along the arm, the adapters areformed to have a general fit on the arm. As a result, the fit istypically loose, thus making it even more difficult to properly positionthe adapter for welding. Digging efficiency is therefore usually lost inthe improper mounting of such teeth to a dredge cutterhead.

In another aspect of the present invention, the arm is formed with aplurality of spaced apart locator formations along the front edge of thearm to properly position the teeth at the desired orientations. Thelocator formations each have the same structural configuration, althoughtheir orientations relative to the surrounding arm contour may differ soas to properly orient each tooth for the particular location along thearm. In one aspect of the invention, a separable base member is providedwith a complementary coupling formation to matingly fit with the locatorformations so as to support and position the adapter properly on thearm. As a result, each base can be formed with the same shapeirrespective_of where along the arm it is to be mounted. Moreover, thesebases are adapted to be positioned on the dredge cutterhead in an easy,accurate and quick manner. In an alternative embodiment of theinvention, a weld-on adapter includes a coupling formation to match thelocator formations provided on the arm so that weld-on adapters can beeasily secured in proper position on the arms. As with the bases of theinvention, these adapters can each be made to have the same shape andeasily positioned correctly irrespective of where along the arm they areto be mounted.

Another aspect of the invention pertains to an improvement in weldingparts to a base surface, such as the arm of an excavator or lip of abucket. The welding of components to a base surface results inconsiderable heating of both the welded part and the base surface. Aseach weld bead cools, it contracts to leave a residual tensile stressalong the sides of the joint, i.e., in the heat affected zone. Thebottom of the joint is defined by the surface of the welded part and thebase surface, which abut each other but are not welded together. Theseunbonded surfaces act as a gap in the union of the components, which inturn, reacts much as a crack when the welded part is loaded. As can beappreciated, loads transferred through the weld joint can produceextremely high stresses at the end of the gap (i.e., at the bottom ofthe weld joint). This is also at the start of the heat affected zone,which is already weakened due to the heat. As a result, any failure inthe connection will often begin at this point.

To improve the strength and integrity of the welding of a part to a basesurface, the bottom surface of the welded part is formed with a groovenear the weld bead. With this construction, as the weld bead cools andcontracts, it draws the lip of the welded part (i.e., the portionoutside of the groove) outward. Now the residual stress is concentratedat the top of the groove, rather than at the end of the gap. The top ofthe groove has a smooth radius, which provides a much lower stressconcentration factor than the sharp end of the gap. It is also formed inthe parent metal of the part, which is stronger than the weld materialat the end of the gap. This construction, then, greatly reduces thetendency of the weld to fail.

The use of a groove in the underside of the welded part can also easeand improve the removal of welded parts from a base surface. Whencutting the welded part away from the base surface with a torch (e.g.,an air arc) the user can more easily follow the groove. In this way, thecontour that remains is very near the original weld prep shape, andlittle clean-up is required before welding on a replacement part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective exploded view of an attachment assembly inaccordance with the present invention.

FIG. 2 is a perspective view of a base in accordance with the presentinvention in conjunction with an imaginary sphere.

FIG. 3 is a top plan view of the base.

FIG. 4 is a side elevational view of the base.

FIG. 5 is a perspective view of a portion of an arm of a dredgecutterhead in accordance with the present invention.

FIG. 6 is a top perspective view of the base positioned on the arm.

FIG. 7 is a rear perspective view of an adapter in accordance with thepresent invention.

FIG. 8 is a side elevational view of the adapter.

FIG. 9 is a top plan view of the adapter.

FIG. 10 is an exploded perspective view of a lock in accordance with thepresent invention.

FIG. 11 is a side elevational view of the lock.

FIG. 12 is a top plan view of the lock.

FIG. 13 is a perspective view of the lock.

FIG. 14 is a cross-sectional view of the lock taken along line XIV-XIVin FIG. 13.

FIG. 15 is a top schematic view of a tooth in accordance with thepresent invention under side loading.

FIG. 16 is a top schematic view of a prior art tooth under side loading.

FIG. 17 is a perspective view of a prior art dredge cutterhead.

FIG. 18 is a perspective view of another prior art dredge cutterhead.

FIG. 19 is a perspective view of a weld-on adapter mounted on a dredgearm in another embodiment.

FIG. 20 is a side view of an alternative weld-on adapter.

FIG. 21 is a cross section of the base and lip without the weld beadtaken along line 21-21 in FIG. 1.

FIG. 22 is an enlarged view of portion A from FIG. 21 with the weld beadincluded.

FIG. 23 is an axial cross sectional view of an alternative wear assemblyin accordance with the present invention.

FIGS. 24 and 25 are perspective views of the base in FIG. 23.

FIGS. 26 and 27 are perspective views of the adapter in FIG. 23.

FIG. 28 is an axial cross sectional view of the adapter in FIG. 23.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention pertains to an assembly for securing a wear memberto an excavator. The present invention is particularly suited formounting a tooth on a dredge cutterhead because of the ability of thetooth in the preferred construction to better withstand heavy transverseloading typical of a dredging operation and dampen rattling of theparts. Nevertheless, a tooth in accordance with the present inventioncould be used with other excavators. Additionally, other wear membersused in excavating equipment (e.g., shrouds) could be mounted using thepresent invention.

In accordance with the present invention, a tooth 30 includes a base ormount 32, an adapter 34, a point (not shown), and a lock 36 (FIG. 1).The tooth components will at times be described in relative terms, suchas up and down, even though the operation of the dredging equipment willcause the teeth to assume many different orientations. These directionsare used for explanation purposes only and should ordinarily beunderstood with respect to the orientation in FIG. 1.

In the preferred construction, base 32 has a lower leg 38, a front body40 and an upper leg 42 in a generally U-shaped configuration (FIG. 14)that wraps around the front edge 44 of an arm 48 of a cutterhead forenhanced support. The base is preferably a cast one-piece product thatis fixed to the arm by welding, but could be mechanically attached orconstructed as a multi-piece component. Alternatively, the base could befixed to the arm as a structure that is cast as a unitary part of thearm (not shown).

Lower leg 38 extends only a short distance along a lower side 47 of arm48, although it may be omitted or provided with an extendedconstruction. Upper leg 42 extends rearward along an upper side 55 ofarm 48 and includes a coupling configuration 56 for securing theadapter. Since the lower or inner side 47 of an arm of a dredgecutterhead is more difficult to access, the coupling configuration ispreferably formed to be on the upper or outer side 55 of the arm.Nevertheless, alternative constructions are possible. For instance, thelegs could be reversed on the arm or a coupling configuration could beprovided on both of the upper and lower sides of the arms. The legs 38,42 and body 40 collectively define an inner surface 54 that faces thearm. To facilitate effective welding of the base to the arm, the innersurface 54 is shaped to substantially conform to the contour of theportion of arm 48 it opposes. The base is welded to the arm alongsubstantially its entire perimeter to securely fix the base to thecutterhead.

In a preferred construction, the inner surface 59 of base 32 setsagainst seats 61 prepared in sides 47, 55 of arm 48. For illustrationpurposes, upper leg 42 of base 32 is shown engaged with seat 61 in side55 of arm 48. While other seats or no seat could be used, seat 61defines a recessed portion in the arm which is slightly wider than thelower end 62 of base 32. The seat defines a main surface 63 and inclinedwalls 67 extending upward to the upper surface 55 of the arm. On accountof the spacing of walls 67, as can be seen in FIG. 21, a trough 81 isdefined along each side of base 32. The trough preferably extends alongthe entire periphery of base 32, but it is not essential that it do so.As is known, a weld bead 82 is placed in trough 81 to secure base 32 toarm 48. The welding process forms a heat affected zone 83 all around theweld bead 82, including a heat affected zone 83 a in base 32 and a heataffected zone 83 b in arm 48. The heat affected zones of the componentsare weakened as compared to the portions outside of the heat affectedzones.

In the preferred construction, upper leg 42 of base 32 includes foot 84and a tongue 57 defined by a stem 85 and rails 87. The undersurface 89of foot 84 sets against main surface 63 of seat 61. While a ridge 91 andvalley 93 is preferably formed along the midpoint of foot 84 forpositioning and additional lateral support, this construction is notessential. Also, the ridge and valley could be reversed.

The undersurface 89 of base 32 is further provided with a groove 95 thatgenerally parallels the outer sidewall 99 of foot 84. As best seen inFIG. 22, groove 95 preferably has an outer wall 95 a that is spaced fromsidewall 99. Outer wall 95 a, at the bottom of groove 95, transitionsinto a rounded dome wall 95 b which, in turn, turns into an inclinedinner wall 95 c. The dome wall 95 b is deemed to be the bottom of thegroove irrespective of the actual orientation of the part. In general,in a preferred construction, the groove is preferably spaced from outerwall 99 of the welded part so as to be just outside of the heat affectedzone, though the groove could be closer or farther from the outer wallso long as the groove is sufficiently far from wall 99 to avoid breakageand sufficiently close to redirect the stress concentrations to thematerial forming the groove. As can be appreciated, the welding processcauses great heating of both base 32 and arm 48 along with the weldmaterial. These portions are considered to have been weakened on accountof this heating. The height H of the groove is variable, but in onepreferred embodiment the height is slightly larger than the thickness ofthe heat affected zone 83a. Similarly, groove 95 can have differentwidth dimensions, but in one preferred construction has a width W thatis about 1½ times larger than the height. As one example only, in a base32 with a foot 84 having a width of 69 mm and a height of 15 mm, thegroove could have a height H of 2.7 mm, a width W of 4.8 mm and bespaced a distance S 2.3 mm from sidewall 99. Numerous variations inshape and size could be used in forming the foot 84 and groove 95.

As the weld bead cools, it contracts to leave a residual tensile stressalong the sides of the joint. The abutment of undersurface 89 againstmain surface 63 defines unwelded surfaces within the uniting of base 32and arm 48 by weld bead 82. These unbonded surfaces define a gap 102 (orthe effect of a gap even if the surfaces are completely flush with eachother), which acts like a crack when under load. As can be appreciated,loads transferred through weld bead 82 can produce high stresses at theend of the gap (i.e., at the bottom of the weld joint). This is also atthe start of the heat affected zone 83, which is already weakened due tothe heat.

The formation of groove 95 near weld bead 82 reduces the stress in theweld. As the weld bead cools and contracts, it draws the lip 111 (i.e.,the portion of foot 84 between outer wall 95 a and sidewall 99) outward.In this way, the residual stress is concentrated at the top of thegroove (i.e., along dome surface 95 b), rather than at the end of gap102. The top of the groove has a smooth radius, which provides a muchlower stress concentration factor than the sharp end of the gap. It isalso formed in the parent metal of the part, which is stronger than theweld material at the end of the gap. This construction, then, greatlyreduces the tendency of the weld to crack. Moreover, in the preferredconstruction, the stress concentration is resisted by material outsideof the heat affected zone.

The provision of groove 95 in the underside of base 32 also eases andimproves the removal of the base from arm 48. When cutting the weldedpart away from the base surface with a torch (not shown), the user caneasily follow the groove by sight. In this way, the contour that remainsafter the cutting is very near the original weld prep shape, and littleclean-up is required before welding on a replacement part. Groove 95preferably extends along the edge portions of the part subject to beingwelded, in the illustrated embodiment it preferably extends along theentire periphery of base 32, but could be less if desired.

While the above-discussion describes the use of a groove in theunderside of a base welded to an arm of a dredge cutterhead, the groovecould be used to secure a base or other welded components to a widearray of excavators including, for example, front end loaders, electricshovels, hydraulic excavators, hydraulic shovels, clamshells, draglines,rock grapples, dragheads and other equipment. As examples only, thegroove could be also be used to attach a weld-on adapter, shroud orother member to an excavator. Furthermore, the use of such a groove canprovide benefits in attaching a wide array of welded parts to a supportsurface in a myriad of different structures inside and outside thedredging, mining and construction industries.

Upper leg 42 extends rearward of body 40 along upper side 55 of the armto define coupling configuration 56 for securing the adapter. Thecoupling configuration is preferably an axial T-shaped tongue 57 thatslidably engages a complementary construction 58 on adapter 34.Nonetheless, other constructions provided with at least one laterallyextending shoulder could be used to couple the adapter and the base. Asexamples, the coupling configuration 56 could be formed as othergenerally T-shaped tongues such as a dovetail tongue and other tonguesthat laterally broaden in a symmetrical manner, other non-symmetricalshaped tongues, or a slot having T, dovetail or other shape. In anyevent, the upper leg preferably extends initially upward above body 40to enable the adapter to slide past the body and couple with the tongue.The rear end wall of upper leg 42 defines a rear bearing surface 60adapted to engage lock 36. As discussed more fully below, the rearbearing surface is preferably curved and most preferably defines aconvex spherical segment (FIG. 2). Nonetheless, a flat rear bearingsurface could be used, albeit with reduced benefits.

The body 40 projects forward from the front edge 44 of arm 48 to resistthe forces applied to the tooth 30 during use. In the preferredconstruction, the body includes sidewalls 50, 52, top and bottom walls64, 66 and a front bearing surface 68. The front bearing surface 68 hasa convex, curved shape, as discussed more fully below, to maintain asubstantially full face contact with a complementary surface on theadapter during transverse loading of the tooth. In the preferredconstruction, front bearing surface 68 defines a convex sphericalsegment (as illustrated by the shaded portion in FIG. 2) to accommodatetransverse loading in any direction, such as, side loads, upward loads,downward loads or virtually any load that applies a force transverse tothe longitudinal axis 69 of the tooth. Nevertheless, bearing surface 68could be formed with a surface that is curved in both horizontal andvertical directions but is not spherical. In this type of constructionthe radii of curvature for either or both curved directions could befixed or variable. Moreover, the bearing surface 68 could be providedwith a curved shape in only one direction, although with reducedbenefits. For instance, bearing surface 68 could be curved in only ahorizontal or vertical direction or in any particular desired direction.However, when curved in only one direction, the desired full facecontact can only be maintained for transverse loading in the samegeneral direction as the curvature of the bearing surface.

The radius (or radii) of curvature defining bearing surface 68 is basedupon the relative gap that exists between the base and the adapter. Forinstance, a clearance is formed between the parts to ensure the adaptercan be coupled to the base, especially along the coupling configuration.When a lateral load is applied to the tooth tip, the adapter will rotateuntil the gaps along the sides close at diagonally opposing cornersforming a couple to oppose the lateral load. If the gap between the baseand the adapter is the same along the front end and the rear end of base32, then the center of rotation of the adapter will be at about the midpoint M of base 32 (i.e., the mid point between bearing surfaces 60,68). However, if the gap is smaller at one end as compared to the otherend, then the center of rotation will be closer to the end with thesmaller gap depending on the amount of the disparity between the parts,i.e., the greater the disparity in the gaps, the greater the center ofrotation shifts toward the end with the smaller gap. In the preferredconstruction, the center of rotation is used as the imaginary centerpoint for the radius of curvature. As can be appreciated, thedifferences in the clearance along the sides could be different than theclearance along the top and bottom of the base and adapter. In thisconstruction, the curvature in the horizontal direction is preferablydifferent than the curvature in the vertical direction so as tocorrespond to the spacing of the different clearances.

In the preferred construction, as shown in FIG. 2, the rear bearingsurface 60 is curved in the same way as front bearing surface 68,although they could be different. Accordingly, the rear bearing surfacecan be varied in the same manner as discussed above for front bearingface 68 (e.g., with curves in one or more directions). Preferably, therear and front bearing surfaces 60, 68 are defined by radii of curvaturethat initiate from the same point that matches the center of rotation ofthe adapter. However, due to unavoidable deflection of the parts underheavy loads, there can be some divergence of the points defining theradii of curvature for the front and rear bearing surfaces. Further,rear bearing surface 60 can have a widely different starting point fordefining the radius of curvature, or it can even be flat, though such aconstruction will impose higher stresses on the lock and rear of thebase. Hence, the front and rear bearing surfaces may have the samecurvature, but also may simply have corresponding curvatures, i.e.,where the radius of curvature originates at the same point even thoughthey may each have different lengths. For example, if the center ofrotation of the adapter, as discussed above, is closer to the rear endthan the front end, then rear bearing surface 60 will preferably have asmaller radius of curvature than front bearing surface 68.

The front edge 44 of arm 48 is preferably provided with a plurality ofspaced apart locator formations 65 for mounting the excavating teeth. Ina preferred embodiment, each locator formation includes a locator nose70 (FIG. 5) that projects from a recess 71. In the preferredconstruction, each locator nose is cast as part of the arm with aparticular shaped core in the mold. The core is placed in the mold inthe orientation needed for positioning each tooth properly on the arm.In this way, there are no difficulties in positioning the adapters onthe arms. The locator noses 70 cast in the arm 48 already provides thedesired orientation for the tooth.

In the preferred construction, the locator nose projects from a recess71 formed in the front edge of arm 48. The trough surfaces 72 in thebottom of the recesses oppose the inner edges 53, 54 of the sidewalls50, 52 of the body of the base preferably leaving a small gap. This gapalso enables the operator to more easily cut the base from the arm ifneeded. A space 73 preferably exists between the outer surfaces 74, 75of sidewalls 50, 52 and the bevel surfaces 76 to accommodate theapplication of a weld. The adapter includes a coupling formation 78 thatinteracts with the locator formations 65 to properly position theexcavating tooth for maximum cutting efficiency. In this construction,the body 40 of base 32 defines a pocket 77 that matingly receives thelocator nose 70 to properly position and support the base on the arm.The side faces 79 and free end face 80 of nose 70 fit againstcomplementary surfaces defining pocket 77 to properly orient the toothon the arm and provide support for the boss in addition to the welds.For this reason, noses 70 preferably have a considerable forwardextension. In a preferred construction, the noses extend approximately1.50 inches beyond trough surfaces 72 and within a range of about 0.75to 2.25 inches. Nevertheless, lesser or greater nose extensions could beused.

The wear member in the form of adapter 34 (FIGS. 1 and 7-9) has a rearportion 86 that mounts to base 32 and a front portion 88 for holding apoint or tip (not shown). In the preferred construction, the frontportion includes a forwardly projecting nose 90 that is received intothe socket of a point. The nose can have any configuration for mountinga point. In this embodiment, the front portion further includes a slot92 for receiving a lock pin (not shown) to hold the point to theadapter. The rear portion 86 includes an upper leg 94, a lower leg 96,and a mid portion 98. Lower leg 96 of adapter 34 overlies bottom wall66. The rear end 97 of leg 96 opposes front wall 101 of the base so thatunder extreme loads wall 101 functions to stop the shifting of theadapter on the base. Upper leg 94 extends rearward to overlie top wall64 and upper leg 42 of base 32. The upper leg of adapter 34 includes acoupling configuration 58 that is adapted to mate with the couplingconfiguration 56 of base 32. Hence, the coupling configuration ofadapter 34 can be varied in the same way as the coupling configurationfor base 32. In the preferred construction, upper leg 94 includes aT-shaped slot 103 that matingly receives T-shaped tongue 57. TheT-shaped slot 103 is open along the inner surface 104 and in the rearwall 106 of upper leg 94 to facilitate receipt of tongue 57. Ribs 107are preferably formed along the inner edge 108 of mid portion 98 forenhanced strength to resist cracking during use (FIGS. 1, 7 and 8).

The mid portion 98 of adapter 34 includes an interior recess 109 havingan abutment or abutting surface 105 adapted to abut front bearingsurface 68 of base 32. Abutment 105 is arcuate and concave in shape tomatch the arcuate front bearing surface 68. Accordingly, abutment 105and bearing surface 68 each preferably define a spherical segment withessentially the same radius of curvature, although the curves coulddiffer within a certain range of values primarily because of deflectionthat occurs in the parts under heavy loading. As discussed above, thepreferred shape of abutment 105 and bearing surface 68 is defined by aradius of curvature that is determined by the clearance between thefront and rear end portions of the adapter and base. In the mostpreferred configuration, the gaps between the base and the adapter areuniform from front to back along the sides and along the top and bottomso that the curved bearing surfaces 68, 105 each define a sphericalsegment. The actual desired size of the radius of curvature defining thespherical segments would depend on the gaps as well as the actual sizeof the part. As a general rule, the radius of curvature definingsurfaces 68, 105 is preferably not larger than the length of base 32(i.e., the distance between rear and front bearing surfaces 60, 68) toavoid having too broad of an arc.

As seen in FIG. 15, a side load L1 tends to rotate adapter 34 relativeto base 32 about a center of rotation C. The radius of curvaturedefining bearing surfaces 68, 105 originate from the same center ofrotation. Because of the mating arcuate configuration of abutment 105and bearing surface 68, these surfaces remain in essentially fullbearing contact with each other. Accordingly, no forces are applied aspoint contacts in the axial direction to prematurely wear the parts.Instead, the axial loads are spread out over substantially the whole ofthe abutment 105 and bearing surface 68 to greatly reduce the stress inthe parts. As a result, the high stresses accompanying resultant forcesR2, R3 (FIG. 16) are essentially eliminated.

Adapter 34 further includes an opening 110 in a rear portion of upperleg 94 (FIGS. 1 and 7-9). In the preferred construction, opening 110 hasa generally rectangular configuration with a curved front wall 113 and acurved rear wall 115. Nevertheless, it is not necessary that the wallsbe curved or that the opening has an overall generally rectangularconfiguration. Rather, the opening can have virtually any shape so longas it receives the lock which, in turn, secures the adapter to the base.If there is any shifting of adapter 34 during use, the lock 36 tends tomove with the adapter. Hence, there is ordinarily no significantshifting between the lock and the adapter and thus no undue wearingtherebetween. Rear wall 115 preferably includes a hole 117 that extendsthrough the rear end 106 of upper leg 94 to accommodate an adjustmentassembly of lock 36. Nevertheless, hole 117 could have a variety ofdifferent shapes or be eliminated if an adjustment assembly is not usedor one is used that does not require the space provided by hole 117.

Lock 36 is adapted to be received in opening 110 (FIGS. 1 and 10-14). Inthe preferred construction, lock 36 has a generally rectangularconfiguration with a curved front wall 123 and a curved rear wall 125 tomatch the configuration of opening 110. Although shifting between theadapter and lock is not likely, the curved walls 115, 125 tend to reduceany wearing in the event shifting occurs. Nevertheless, lock 36 may havea varied shape in the same way as discussed above for opening 110.

In the preferred construction, lock 36 comprises an outer part 127, aninner part 129, a resilient member 131 and an actuator, preferably inthe form of a screw 133. Outer part 127 defines a cavity 134 forreceiving the inner part 129 and resilient member 131. In general, outerpart 127 is generally C-shaped to include a base wall 135, a top wall137 and a bottom wall 139. A pair of lips 141, 143 extends toward eachother from the top and bottom walls 137, 139 to contain the inner part129 and resilient member 131 in cavity 134. Base wall 135 includes anaperture 136 for receiving screw 133. The inner part also has agenerally C-shaped configuration with a center wall 147 and twosidewalls 149. The two C-shaped components fit together to generallydefine a box-like shape. In the preferred curved construction, sidewalls149 are at obtuse angles to center wall 147 to match the side edges 150of outer part 127. An internally threaded boss 151 extends rearward fromthe center of center wall 147 to receive screw 133. Resilient member 131is preferably an elastomer. In the preferred construction, the elastomeris composed of neoprene or rubber, although other types of elastomericmaterials can be used. The elastomer is shaped for receipt in inner part129 about boss 151. In the preferred embodiment, resilient member 131has a base portion 132 with an aperture 138 and a pair of arm portions142. Nevertheless, other shapes could be used. Moreover, other kinds ofresilient members could be used, such as Bellville springs or a coiledspring.

The lock is assembled by placing the resilient member 131 about boss 151in inner part 129. The combined inner part and resilient member are theninserted laterally into the side of cavity 134 in outer part 127, i.e.,by side edges 150. Once boss 151 is aligned with aperture 136, screw 133is preferably back threaded into boss 151 until it is received intoaperture 136. The screw ensures that the component parts do not becomeinadvertently disassembled.

In use, lock 36 is inserted into opening 110 after adapter 34 is placedover base 32 with tongue 57 received in slot 103 (FIG. 1). Screw 133includes a head 153 with some means for engaging a tool (not shown) forturning the screw. In the preferred embodiment, screw head 153 hasinternal flats 155 for receiving an appropriate wrench. The free end ofscrew 133 includes a bearing surface 157 that abuts rear bearing surface60 when the screw is advanced.

Further advancement of screw 133 against rear bearing surface 60 causesthe rear face 125 of base wall 135 to push rearwardly against the rearwall 115 of opening 110. This expansion of the lock results in abutment105 of adapter 34 being brought into tight abutting relationship withfront bearing surface 68 of base 32. Further advancement of screw 133following such abutment will then cause the inner part 129 to movetoward the outer part 127 to compress resilient member 131 untilsidewalls 149 abut base wall 135. The sidewalls will abut base wall 135to prevent over-compression of the resilient member. If the elastomer isa non-compressible rubber material or the like, there is enough openspace between the inner and outer parts to permit the inner part 129 tobe drawn against the outer part 127. Depending on the resistance incoupling the adapter to the base, the resilient member may compress insome instances before the adapter is fully tightened onto the base. Inany event, with inner part 129 in abutting contact with outer part 127,lock 36 initially is a rigid lock member. As wear begins to developbetween adapter 34 and base 32, resilient member 131 expands to dampenmovement of the adapter relative to the base and maintain a tightrelationship between the components of the tooth. This expansion of lock36 continues to hold the components tightly together until resilientmember 131 reaches its fully expanded position (i.e., when the innerpart abuts against lips 141, 143).

Bearing surface 157 on screw 133 preferably has a concave, arcuatesurface to engage the corresponding rear bearing surface 60 (FIG. 14).In the most preferred construction, bearing surface 60 and 157 are eachformed as a spherical segment. In this way, bearing surface 157 remainsin substantially full contact with rear bearing surface 60 as adapter 34shifts under transverse loading (i.e., as the adapter rotates about itscenter of rotation). While bearing surfaces 60 and 157 can be formedwith the same radius of curvature, bearing surface 157 of screw 133 canalternatively be formed with a smaller radius of curvature so as tocontact rear bearing surface 60 with a circular contact. The sphericalconfiguration of the rear base surface still enables the circle contactof screw 133 to remain in substantially full contact with base 32 duringany shifting of the adapter.

Alternatively, other locks could be used so long as they abut adapter 34and base 32 so as to prevent the adapter from sliding forwardly off ofthe base. For example, a lock with a different adjustment assembly couldbe used, such as the fluid actuator as disclosed in U.S. Pat. No.5,653,048 to Jones et al., herein incorporated by reference. Similarly,an opening and lock such as disclosed in U.S. Pat. No. 5,088,214 toJones et al., herein incorporated by reference, without an adjustmentassembly could also be used.

In an alternative construction, weld-on adapters 175 can be mounted onthe locator formations 65 of the dredge cutterhead arm 48 without bases32 (FIG. 19). While the use of such adapters does not provide the easyremoval and installation procedures of the mechanically attachedadapters discussed above, the locator formations still provide easypositioning of the adapters as well as additional support. In apreferred construction, adapters 175 include a pair of bifurcated legs177, 178 that straddle the arm, although a single leg could be used (notshown). If a single leg is used, the leg will preferably be located onthe upper side of the arm to enable easier welding of the adapter to thearm. The adapter includes a coupling formation 180 to matingly fit withthe locator formations 65 so as to properly position the adapter, andthus, the tooth point (not shown) for maximum digging efficiency. Aswith base 32, adapters 175 include a pocket 183 that matingly receivesnose 70 with surfaces that oppose side faces 79 and end face 80 toproperly position and support the adapter in use. The adapter is thenwelded along all or parts of its periphery. Also, as with boss 32, theadapter is preferably spaced from the trough surfaces 72 for easierremoval of the adapter from the arm.

In another alternative construction, adapter 175 a includes a couplingformation 180 a that does not rely upon nose 70 for positioning andsupport (FIG. 20). In this arrangement, each locator formation includesa pair of spaced apart surfaces having a particular shape and spacing toengage, support and properly position a wear member. For example, troughsurfaces 72 to each side of nose 70 are formed with a shape that matchesthe inner edge surfaces of the bight 185 a interconnecting legs 177 a,178 a. The bight surface 185 a, then, sets against trough surfaces toproperly orient the tooth. An adapter with coupling formation 180 a caninclude an enlarged pocket 183 a that does not engage nose 70 or can beused with an arm that does not include a nose 70.

In another alternative construction, another weld-on adapter can be fitover base 32. In this construction, the adapter includes a pocket thatmatingly receives body 40 and includes a configuration, such as arecess, that enables the arm to fit over but not connect to the tongueof base 32. Alternatively, a base without a leg or with a leg having nocoupling tongue could be used with such a weld-on adapter. In eithercase, the body 40 of base 32 properly orients and provides support tothe adapter, which is then welded to the arm.

In another alternative construction (FIGS. 23-28), wear assembly 230 issecured to arm 48. As with assembly 30, assembly 230 is described interms of mounting an adapter on a cutterhead, but it could be used tosecure other wear members to other excavating equipment. Assembly 230includes a base 232 fixed to arm 48 by welding, mechanical attachment orby being cast with the arm, and a wear member or adapter 234 fit overthe base. Base 232 and adapter 234 are similar to base 32 and adapter 34in construction and purpose, and are essentially the same except asdescribed below.

Base 232 includes a front bearing surface 268 to engage a complementaryabutting surface 305 of adapter 234 to primarily resist the heavy axialloading applied to tooth 230 during use. As discussed above in regard toassembly 30, bearing surface 268 and abutment 305 are curved, preferablyabout two perpendicular axes. However, unlike assembly 30, bearingsurface 268 and abutment 305 are divided into sections by front stops350, 351. In particular, bearing surface 268 includes a first section268a above stop 350 and a second section 268 b below stop 350. Likewise,abutting surface 305 is divided into a first section 305 a above stop351 and second section 305 b below stop 351. In a preferred embodiment,bearing surface 268 a and abutting surface 305 a have complementarysurfaces that conform to a spherical segment. Likewise, bearing surface268 b and abutting surface 305 b have complementary surfaces thatconform to a spherical segment, but one which is concentric to bearingand abutting surfaces 268 a, 305 a. In this way, sections 268 a, 268 b305 a, 305 b function essentially as unified front bearing and abuttingsurfaces 268, 305 in resisting the axial loading.

As described above for assembly 30, the curved bearing and abuttingsurfaces 268, 305 enable to the parts to move relative to each otherunder load without creating undue stress concentrations in the cornersof the components as in the past. Unrestricted motion between thecomponents, however, can lead to undesirable wear rates. Loads withupward components are, without front stops 350, 351, resisted primarilyby lower faces 370, 371 and by the tongue and slot arrangement 257, 303.However, flexing of the adapter 234 causes faces 305 a, 305 b to slidealong faces 268 a, 268 b. The relative movement between the base and theadapter can be significant and lead to premature wearing of bothcomponents. The provision of stops 350, 351 at the front of the base(i.e., where the sliding occurs) and extending generally transverse tothe direction the adapter rocks over the base is effective in resistingand reducing such relative motion and, in turn, reducing wearing of thecomponents.

Flexing of leg 294 caused by upward loading of tooth 230 also tends toslide upper leg 294 of adapter 234 axially along leg 242 of base 232.However, complementary stops 355, 356, 360, 361 are preferably providedto resist such relative sliding of legs 242, 294. In a preferredconstruction, base 232 includes axially spaced stops 355, 360 along leg242. A medial stop 355 projects upward at a medial portion of base 232,preferably around the intersection of legs 238, 242 (although otherpositions are possible), and a rear stop 360 projects upward proximaterear wall 260. Adapter 234 includes a recess 309 to at least partiallyreceive base 232, and an opening 310 to receive lock 36 (FIG. 23).Recess 309 includes a plurality of complementary stops 356, 361 to abutstops 355, 360, respectively (FIGS. 23 and 26-28). Stops 356, 361 are to(i) be generally transverse to the axis and expected sliding of the leg,(ii) provide additional surface area to better resist rocking of adapter234 under upward loads, and (iii) be spaced apart along the leg tobetter reduce relative shifting of all portions of the adapter underupward loading. While stops 355, 356, 360, 361 are intended tosupplement front stops 350, 351, it is possible to rely upon only one ora pair of the front, medial or rear stops.

Base stops 355, 360 and adapter stops 356, 361 define tiers orstair-steps to resist the upward loads without unduly enlarging the sizeof the assembly and to facilitate easy casting of the component. Forexample, medial stop 355 extends farther from arm 48 than the frontbearing surface 268, and rear stop 360 extends farther from arm 48 thanmedial stop 355. Stops 355, 356, 360, 361 could be laterally spacedrelative to each other, instead of or in addition to being verticallyspaced, in their medial and rear positions. Stops 355, 356, 360, 361 arepreferably planar, but could alternatively be arcuate or conformed to aspherical segment. Moreover, stops 355, 356, 360, 361 can be vertical orsomewhat inclined so long as they are generally transverse to theexpected direction of shifting of the component.

For downward loads, lower leg 238 of base 232 includes a lower stop 365adapted to abut complementary stop 366 formed on the end of lower leg296 of adapter 234. In the same way as described for stops 355, 356,360, 361 for upward loading, stops 365, 366 resist rocking of theadapter on the base for downward loading.

The above-discussion concerns the preferred embodiments of the presentinvention. Various other embodiments as well as many changes andalterations may be made without departing from the spirit and broaderaspects of the invention as defined in the claims.

1. A wear member for mounting on a base fixed to excavating equipment,the wear member comprising: a front end; a curved abutting surface forabutting a front bearing surface of the base; a rearwardly extending legincluding an axial slot to receive a tongue of the base; an opening forreceiving a lock to releasably secure the wear member to the base; and astop extending generally transverse to the abutting surface andsubdividing the abutting surface into a plurality of sections, the stopabutting a complementary stop on the base to resist movement of the wearmember on the base under certain loading conditions.
 2. A wear member inaccordance with claim 1 wherein the abutting surface is curved about twoperpendicular axes.
 3. A wear member in accordance with claim 2 whereina first section of the abutting surface is concentric to a secondsection of the abutting surface.
 4. A wear member in accordance withclaim 1 wherein the abutting surface generally conforms to a sphericalsegment.
 5. A wear member in accordance with claim 4 wherein a firstsection of the abutting surface is concentric to a second section of theabutting surface.
 6. A wear member in accordance with claim 5 furtherincluding at least one stop projecting from the leg in a generallytransverse direction relative to the leg.
 7. A wear member in accordancewith claim 6 wherein said at least one stop includes a rear stoppositioned in a rear portion of the wear member.
 8. A wear member inaccordance with claim 7 wherein said at least one stop includes a medialstop positioned in a mid portion of the wear member.
 9. A wear member inaccordance with claim 8 further including a second leg, wherein one saidleg is an upper leg with said rear and medial stops, and the second legis a lower leg provided with a lower stop.
 10. A wear member inaccordance with claim 6 wherein said at least one stop includes a medialstop positioned in a mid portion of the wear member.
 11. A wear memberin accordance with claim 6 further including a second leg, wherein saidone leg is an upper leg with one said stop, and the second leg is alower leg provided with one said stop.
 12. A wear member in accordancewith claim 1 further including at least one stop projecting from the legin a generally transverse direction relative to the leg.
 13. A wearmember in accordance with claim 12 further including a second leg,wherein said one leg is an upper leg with one said stop, and the secondleg is a lower leg provided with one said stop.
 14. A wear member inaccordance with claim 1 wherein the front end includes a nose formounting a point.
 15. A wear member for mounting on a base fixed toexcavating equipment, the wear member comprising: a front end; a curvedabutting surface for abutting a front bearing surface of the base; atleast one rearwardly extending leg including an opening to receive alock to retain the wear member to the base, an axial slot to receive atongue of the base, and at least one stop extending generally transverseto the leg between the opening and the abutting surface to abut acomplementary stop on the base and resist movement of the wear member onthe base under certain loading conditions.
 16. A wear member inaccordance with claim 15 wherein said at least one stop includes a rearstop proximate the opening and a medial stop proximate the front bearingsurface.
 17. A wear member in accordance with claim 16 wherein saidstops are arranged in a tier along the leg.
 18. A wear member inaccordance with claim 15 further including another leg provided with astop extending generally transverse to the leg between the opening andthe abutting surface to abut a complementary stop on the base and resistmovement of the wear member on the base under certain loadingconditions.
 19. A wear assembly for excavating equipment comprising: abase fixed to the excavating equipment, and including a front curvedbearing surface, a rearwardly extending tongue, and a stop extendinggenerally transverse to the front bearing surface and subdividing thefront bearing surface into a plurality of sections; a wear memberincluding a front end, a curved abutting surface for abutting the frontbearing surface of the base, at least one rearwardly extending legincluding an axial slot to receive the tongue of the base, an opening,and a stop extending generally transverse to the abutting surface,subdividing the abutting surface into a plurality of sections, andabutting the stop of the base to resist movement of the wear member onthe base under certain loading; and a lock received in the opening toreleasably hold the wear member to the excavating equipment.
 20. A wearassembly in accordance with claim 19 wherein the wear member furtherincludes at least one stop projecting from the leg in a generallytransverse direction relative to the leg.